Design of a Voltage-Conveyor Based Read-Out Circuit for ECG Monitoring

This paper presents the design of a VCII-based read-out circuit for ECG monitoring employing second generation voltage conveyors (VCIIs) as active blocks. Starting from a quick overview of VCII, the paper describes the whole interface, composed by three active blocks and one passive filter, and its basic operation. The proposed circuit was simulated by LT-SPICE firstly designing the internal blocks at transistor level, in 0.18 μm standard CMOS technology, and then using the commercially available device AD844 to demonstrate the validity of the designed circuit also with experimental measurements. The voltage gain is tunable by changing some resistance values in the different stages of the amplifier. In the proposed solution, the differential voltage gain has been set to more than 60 dB, while the common mode gain is about −25 dB. The aim of this research is to test the performance of biological signal amplifiers using the current-mode approach (in particular, VCII) which is still underutilized in this context.